Polymer thickened lubricating greases and their preparation are known in the art. In U.S. Pat. No. 3,392,119, a grease is described comprising a white mineral oil that has been thickened by means of a copolymer of ethylene and a homopolymer of polypropylene. In U.S. Pat. No. 3,850,828, a lubricating grease composition has been described which is thickened with a polymeric mixture comprising a polyethylene and an atactic polypropylene. In EP 0700986 A2, a polymeric thickener for lubricating grease compositions is disclosed comprising containing a mixture of copolymers or homopolymers of polypropylene having a high molecular weight and a copolymer or homopolymer of propylene having a low molecular weight. Further, In EP 0942063, a lubricating grease composition is described comprising at least one polyolefin component, at least one base oil component and at least one rubber component.
A problem associated with grease compositions is that they are often not mechanically stable during the application it is intended for. Hence, not all polymer-thickened grease compositions show an acceptable mechanical stability during use.